This invention relates generally to self-cleaning strainers, and in particular to strainers that are adapted to strain liquid being pumped out of a body of liquid, such as water being pumped out of a pond.
When water is to be pumped out of certain bodies of water, such as an outdoor pit, reservoir, pond, stream, or canal, it is important to prevent debris, such as leaves, sticks, discarded plastic and paper articles, stones, etc., from entering the pump. Rotary self-cleaning strainers that contain cylindrical screens for performing the straining function are often used for this purpose.
Such a strainer is attached to the end of a conduit and placed in the body of water that is to be pumped. The pump is operated to suck water through the strainer and conduit, as the strainer screen prevents debris from being sucked into the conduit along with the water. Certain debris may adhere to the screen""s exterior due to the pump suction force. However, the continued adherence of such debris to the screen""s exterior, and resulting impairment of flow through the screen, are prevented by rotating the screen past a nozzle structure which is disposed on the interior of the screen and directs water outwardly through the screen to dislodge the debris. The water is fed under pressure to the strainer through a separate supply line that may be tapped into the pump""s outlet. The water acts on only a limited circumferential zone of the screen at any given time to force adhering debris away from the exterior of the screen as the screen revolves past the nozzle structure. The remainder of the screen serves to pass the flow of water that is being sucked by the pump.
Because the screen rotates, the strainer cannot lie flat on its side on the bed of the body of water in which it is submerged. Hence, it is disposed in a more or less upright orientation. The pump suction is applied through a suction tube, or pipe, that passes centrally through the strainer and has openings in its side wall through which water that has passed through the screen is sucked into the tube. Because all suction tube openings must be submerged for water to be pumped, and because of the generally upright orientation that is required for the strainer, such a strainer will be unable to pump water out of a body below a certain water level.
Various commonly assigned U.S. Patents, such as U.S. Pat. Nos. 4,822,486; 5,108,592; 5,215,656; 5,356,532; 5,520,808 disclose rotary self-cleaning strainers of this general type.
Another type of self-cleaning strainer that is capable of pumping shallower bodies of water is a shallow water strainer. A known self-cleaning shallow water strainer is described in a document in the accompanying Information Disclosure Statement. That strainer comprises a housing having a circular cylindrical side wall that is closed at its lower end by a circular bottom wall, or floor. A circular screen closes the upper end of the housing side wall. A rotary spray arm is disposed within the housing interior to rotate about a vertical centerline of the housing. The housing side wall contains a through-hole to which a suction pipe on the exterior of the housing is fit. The suction pipe is connected through a pipe, or conduit, to a pump. A supply conduit, or pipe returns some of the pumped water under pressure to the spray arm.
As the pump operates, suction is applied through the suction pipe to the interior of the strainer, drawing water from the interior of the strainer and through the suction pipe. At the same time, pressurized water is returned to the spray arm through the supply conduit. The pressurized water is emitted from the spray arm in a manner that is effective both to dislodge from the screen, debris that is drawn against the exterior of the screen by the suction force of the pump, and to rotate the spray arm. Because the spray arm is cleaning only a limited area of the screen at any given instant, water can be sucked through other areas of the screen into the strainer interior. Because of the spray arm rotation however, adhering debris is being continually dislodged from the screen exterior over the full screen area.
The present invention relates to a strainer that is well suited for immersion in liquid, especially shallow water, to prevent debris, such as leaves, sticks, discarded plastic and paper articles, stones, etc., from entering a pump that is sucking the liquid through the strainer. The strainer is attached to the end of a conduit and immersed in a body of water. The pump is operated to suck water through the strainer and conduit, while a screen of the strainer prevents debris from being sucked through it and into the conduit along with the water. Certain debris may adhere to the screen""s exterior due to the pump suction force. However, the continued adherence of such debris to the screen""s exterior, and resulting impairment of flow through the screen, are prevented by a rotating spray bar that contains nozzles and is disposed within the interior of the strainer to spray water against the screen. The water is fed under pressure to the spray bar through a separate supply line which may be tapped into the pump""s outlet. The spray bar nozzles are aimed to direct water generally upward through the screen dislodging the debris and to cause the spray bar to rotate. Hence, as the spray bar spins, the water washes substantially the full face of the screen.
The present invention provides a number of improvements in a self-cleaning shallow water strainer where water is sucked through a screen that closes the top of a walled strainer housing and a rotating spray arm on the interior of the housing continually cleans the screen.
One aspect of the present invention relates to a self-cleaning strainer that has constructional features that contribute to improvements both in the fabrication and in the performance of the strainer. Polymeric pipes and tubes are used in the fabrication of certain parts of the strainer. Polymeric material is tough and durable, and it is commercially available in various sizes. Various parts are assembled in ways that contribute to overall strength of the finished strainer.
Briefly, the present invention relates to a self-cleaning strainer having a walled housing that encloses an interior space. A straining screen is disposed in covering relation to an opening in the walled housing. The pump sucks liquid from the body of debris-containing liquid into the interior space. A spray mechanism is disposed within the interior space and comprises a spray arm supported for rotation about an axis. The spray mechanism has an inlet via which fluid under pressure is introduced into the spray mechanism and conveyed through the spray arm to outlets spaced apart along the spray arm. The fluid introduced to the spray mechanism inlet under pressure is conveyed through the spray arm to cause the spray arm to rotate about the axis and to be emitted from the spray arm outlets against the screen as the spray arm rotates. A walled suction tube has a portion of its length that contains at least one inlet to the suction tube disposed within the interior space so as to be immersed in liquid within the interior space and continues from that portion through the walled housing to an outlet for communication to pump suction to provide for liquid to be sucked from the interior space through the suction tube.
The axis about which the spray arm rotates is transverse to the portion of the length of the suction tube disposed within the interior space. The spray mechanism is supported on a wall of the housing opposite the straining screen, and a wall of the portion of the suction tube length disposed within the interior space comprises an opening through which the spray mechanism extends from the wall of the housing on which the spray mechanism is supported. The housing comprises a circular cylindrical polymeric side wall having one open end and a circular polymeric end wall that closes the opposite end of the side wall. The straining screen is disposed in covering relation to the one open end of the side wall.
The foregoing features, advantages, and aspects of the invention, along with additional ones, will be seen in the ensuing description and claims, which are accompanied by drawings. The drawings disclose a presently preferred embodiment of the invention according to the best mode contemplated at this time for carrying out the invention.